1. Technical Field
The present disclosure relates to light-emitting devices such as organic electroluminescence devices.
2. Description of the Related Art
Organic electroluminescence devices (hereinafter, written as “organic EL devices”) typically include an anode, a cathode and an electroluminescent layer disposed between the electrodes. The electroluminescent layer includes organic EL materials. Double-side-emission organic EL devices emit light from both the anode side and the cathode side, whilst in single-side-emission devices, light is emitted from only one of these electrode sides.
Single-side-emission organic EL devices typically include a transparent electrode through which light is emitted, and a metal electrode which serves as a reflective layer.
However, the light extraction efficiency is decreased by the absorption of light by the metal electrode and also by the loss of surface plasmon at the metal electrode. Here, the term “light extraction efficiency” in an organic EL device indicates the ratio of the number of photons released from the light extraction surface of the organic EL device to the atmosphere, relative to the number of photons generated in the electroluminescent layer.
Japanese Patent No. 4742880 and Japanese Unexamined Patent Application Publication No. 2011-233288 disclose single-side-emission organic EL devices including a pair of transparent electrodes and a reflective layer disposed opposite to the light extraction surface.
There has been a demand that the light extraction efficiency of light-emitting devices such as organic EL devices be further enhanced.